The most Earth-like planet ever discovered is circling a star 600 light years away, a key finding in an ongoing quest to learn if life exists beyond Earth, scientists said on Monday.
The planet, called Kepler-22b, joins a list of more than 500 planets found to orbit stars beyond our solar system. It is the smallest and the best positioned to have liquid water on its surface -- among the ingredients necessary for life on Earth.

"We are homing in on the true Earth-sized, habitable planets," said San Jose State University astronomer Natalie Batalha, deputy science team lead for NASA's Kepler Space Telescope that discovered the star.

The telescope, which was launched three years ago, is staring at about 150,000 stars in the constellations Cygnus and Lyra, looking for faint and periodic dimming as any circling planets pass by, relative to Kepler's line of sight.

Results will be extrapolated to determine the percentage of stars in the Milky Way galaxy that harbor potentially habitable, Earth-size planets.

This is the first detection of a potentially habitable world orbiting a Sun-like star, scientists reported in findings to be published in The Astrophysical Journal.

Kepler-22b is 600 light years away. A light year is the distance light travels in a year, about 6 trillion miles (10 trillion km).

Ground telescopes
Planets about the same distance from their parent stars as Earth take roughly a year to complete an orbit. Scientists want to see at least three transits to be able to rule out other explanations for fluctuations in a star's light, such as small companion stars. Results also are verified by ground and other space telescopes.
Kepler-22b, which is about 2.4 times the radius of Earth, sits squarely in its star's so-called "habitable zone," the region where liquid water could exist on the surface. Follow-up studies are under way to determine if the planet is solid, like Earth, or more gaseous like Neptune.
"We don't know anything about the planets between Earth-size and Neptune-size because in our solar system we have no examples of such planets. We don't know what fraction are going to be rocky, what fraction are going to be water worlds, what fraction are ice worlds. We have no idea until we measure one and see," Batalha said at a news conference at NASA Ames Research Center in Moffet Field, California.

If Kepler-22b has a surface and a cushion of atmosphere similar to Earth's, it would be about 72 degrees Fahrenheit (22 C), about the same as a spring day in Earth's temperate zone.
Among the 2,326 candidate planets found by the Kepler team, 10 are roughly Earth-size and reside in their host stars' habitable zones.

Another team of privately funded astronomers is scanning the target stars for non-naturally occurring radio signals, part of a project known as SETI, or the Search for Extraterrestrial Intelligence.

"As soon as we find a different, a separate, an independent example of life somewhere else, we're going to know that it's ubiquitous throughout the universe," said astronomer Jill Tarter, director of the SETI Institute in Mountain View.

The Kepler team is meeting for its first science conference this week.

To date, its mass and surface composition remain unknown. If it has an Earth-like density (5.515 g/cm3) then it would mass 13.8 Earths while its surface gravity would be 2.4 times Earth's. If it has water like density (1 g/cm3) then it would mass 2.5 Earths and have a surface gravity of 0.43 times Earth's.

You can't just "get used to" it. Without bionics, exoskeletons and other gimmicks it'd be really hard. When the gravity is x2.4 it's a big number. Let's take Jupiter. A helluva big thing.

Jupiter's volume is that of about 1,321 Earths, yet the planet is only 318 times as massive.

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So Jupiter is 318 times heavier than Earth while Jovian surface gravity is 2.5 times stronger than Earth's gravity, hence its gravitational acceleration is about 25 m/s2. Same thing would be for Kepler-22b.

There's no mention of mass. Gravity could actually be 5.76 times lower* than that on Earth, if mass was exactly the same, which granted, is not likely. Anyway without knowing the mass there's absolutely no way to tell the gravity.

* Remember that gravity is proportional to the product of the two masses and inversely proportional to the square of the distance.

Regarding Jupiter: its mass is 318 times the Earth, but it's radius is ~11 times bigger, that's why its surface gravity is ~2.5 times bigger. 318/11^2 = 2.6 <-- Math is not compltely correct since I rounded up too many numbers, but you get the idea.

So can you travel faster than the speed of light or are you just >600 years old?

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Two points.

The first is that at relativistic speeds the aging process is slowed, in the frame of the "stationary" Earth perspective. As such, he could have experienced less than a few years of travel, but be >600 years old. Silly relativity.

The second, the name is qubit. Maybe he entangled two bodies on a quantum level, transferred his conscience, then dissolved the entanglement. Not really travel perse, but definitely long distance fun.

You can't just "get used to" it. Without bionics, exoskeletons and other gimmicks it'd be really hard. When the gravity is x2.4 it's a big number. Let's take Jupiter. A helluva big thing.

So Jupiter is 318 times heavier than Earth while Jovian surface gravity is 2.5 times stronger than Earth's gravity, hence its gravitational acceleration is about 25 m/s2. Same thing would be for Kepler-22b.

The weight of an object is the force on the object due to gravity. It is the product of the mass m of the object and the magnitude of the local gravitational acceleration g. F=mg

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Stronger gravity = bigger weight = faster g

In everyday practical usage, including commercial usage, the term "weight" is commonly used to mean mass, which scientifically is an entirely different concept. On the surface of the Earth, the acceleration due to gravity (the "strength of gravity") is approximately constant; this means that the ratio of the weight force of a motionless object on the surface of the Earth to its mass is almost independent of its location, so that an object's weight force can stand as a proxy for its mass, and vice versa.

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So if Kepler 22-b's g = Earth's g x 2.4 then human wouldn't feel "comfortable" there. Because all human body / "physics" (blood pressure, organs' positions etc) is designed for our local g. On that planet everything would fall x2.4 faster. Aka that planet has a different "game engine" lol. TBH I dunno do professional astronauts get trained for stronger gravity or only for microgravity.

It's in the habitable zone, yes. It's bigger than Earth, yes.
But mass is not known, density is not known, so gravity could be more or less than ours.
It's a 'super-earth' so it could possibly end up being a mini-neptune, not just a rocky planet with some water. Or it could be completely covered with water/ice.